I have a Dell 8250 that uses RDRAM 16-bit 184 pin NON-ECC. Don't know if this makes a difference, buy I do know that Dell boards don't like just any old RDRAM. You are best to go with what Dell sells or SAMSUNG.
Dell 8250, i850e 4xAGP 2.4ghzCPU 512mbPC1066RDRAM 120gb & 200gbATA
GeF4MX420 SBL5.1 SamSung48xCDRW LiteOn851SDVDRW
RJ-45 to Compaq 9660, 233mhzCPU 104mbFPRAM 12mbVoodoo2 Win95a